The Supermarine B.12/36 was a British prototype four-engine heavy bomber design that was destroyed by enemy action before completion during the

Second World War World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

Design and development

In 1936 the

Air Ministry The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force and civil aviation that existed from 1918 to 1964. It was under the political authority of the ...

issued specification B12/36, its first for a four-engined heavy bomber for the

Royal Air Force The Royal Air Force (RAF) is the Air force, air and space force of the United Kingdom, British Overseas Territories and Crown Dependencies. It was formed towards the end of the World War I, First World War on 1 April 1918, on the merger of t ...

. Supermarine, among others, were invited to tender a design. Supermarine's design, the Type 316, was a single-spar, mid-wing aircraft; the leading edge was swept back but the trailing edge was straight. Bombs were carried in both the wings and the fuselage and defensive armament was in three turrets. Of the different powerplants suggested for the Type 316, there were three of more than 1,000 hp (746 kW): the

Rolls-Royce Merlin The Rolls-Royce Merlin is a British Coolant#Liquids, liquid-cooled V12 engine, V-12 Reciprocating engine, piston aero engine of 27-litre (1,650 cu in) Engine displacement, capacity. Rolls-Royce Limited, Rolls-Royce designed the engine an ...

, the

Bristol Hercules The Bristol Hercules is a 14-cylinder two-row radial aircraft engine designed by Sir Roy Fedden and produced by the Bristol Engine Company starting in 1939. It was the most numerous of their single sleeve valve ( Burt-McCollum, or Argyll, ty ...

radial engine and the Napier Dagger. The aircraft's estimated maximum speed was between and the estimated cruising speed was . The estimated operating ceiling was around and range was . The different proposals were considered by the Air Ministry in late 1936. The 316 was initially low down in the list of preferred designs behind Vickers, Boulton Paul and Armstrong Whitworth but by January 1937 it had been selected as the preferred choice. Both the Air Ministry and Supermarine initiated changes to the design, giving it a larger wing area and a twin tail unit. This revised design was the Type 317 and two prototypes with Hercules engines were ordered on 22 March 1937. The Short S.29 was considered as a backup but re-design work was requested and in June the Air Ministry decided to order prototypes of that also. The death of the 316's chief designer R. J. Mitchell had made the Supermarine design riskier. Supermarine continued with design work for a Merlin engined version – the Type 318. In July 1937 Supermarine were told to stop work on the 318 to concentrate on the 317. While still under construction, the two prototypes and the construction plans were effectively lost when the Supermarine Works at Woolston was bombed by the ''

Luftwaffe The Luftwaffe () was the aerial warfare, aerial-warfare branch of the before and during World War II. German Empire, Germany's military air arms during World War I, the of the Imperial German Army, Imperial Army and the of the Imperial Ge ...

'' on 26 September 1940. The Air Ministry formally cancelled the order in November. The Short S.29 was accepted into service as the

Short Stirling The Short Stirling was a British four-engined heavy bomber of the Second World War. It has the distinction of being the first four-engined bomber to be introduced into service with the Royal Air Force (RAF) during the war (the earlier Handley ...

and was the principal British four-engine heavy bomber until eclipsed by the

Handley Page Halifax The Handley Page Halifax is a British Royal Air Force (RAF) four-engined heavy bomber of the Second World War. It was developed by Handley Page to the same specification as the contemporary twin-engine Avro Manchester. The Halifax has its or ...

and

Avro Lancaster The Avro Lancaster, commonly known as the Lancaster Bomber, is a British World War II, Second World War heavy bomber. It was designed and manufactured by Avro as a contemporary of the Handley Page Halifax, both bombers having been developed to ...

, both coming out of specification B13/36 for a twin-engined bomber.

Specifications (Type 317 estimated performance)

Notes and references

RJ Mitchell. A life in aviation
accessed 13 March 2008 * Buttler, Tony ''British Secret Projects: Fighters & Bombers 1935-1950'' Midland Publishing.

External links

{{DEFAULTSORT:Supermarine B.12 36 1930s British bomber aircraft B.12 36 Mid-wing aircraft Four-engined tractor aircraft Four-engined piston aircraft Aircraft with retractable conventional landing gear Twin-tail aircraft Cancelled military aircraft projects of the United Kingdom Unflown aircraft